1. Field of the Invention
The present invention relates to an apparatus for compensating image vibrations of an image pickup apparatus such as a video camera.
2. Description of the Related Art
An apparatus for compensating image vibrations caused by vibrations such as tremors of the operator""s hands has been practically utilized for an image pickup apparatus such as a video camera. One of compensation methods is achieved through providing an image pickup apparatus with a detection apparatus for detecting vibrations of the image pickup apparatus and an optical compensation system for changing an angle of deflection of the optical axis by changing the apex angle of a prism, for example. The optical compensation system is controlled by a servo circuit based on the output of the detection apparatus and the angle of deflection of the optical axis is thereby controlled. For example, an angular velocity sensor such as a gyro sensor is used for the detection apparatus for detecting vibrations of the image pickup apparatus in this method.
When vibrations are detected by the detection apparatus such as an angular velocity sensor as described above, signals outputted from the detection apparatus include signals resulting from intentional panning (turning a video camera and so on in the lateral direction) and tilting (turning a video camera and so on in the vertical direction) besides signals resulting from vibrations to be compensated such as those caused by tremors of the operator""s hands. Consequently, compensation for image vibrations is performed until the angle of deflection of the optical axis reaches the limit of the compensation range in a short time after intentional panning or tilting is started. As a result, the angle of deflection of the optical axis is fixed to the limit of the compensation range. On completion of panning or tilting the angle of deflection of the optical axis is required to be returned to the neighborhood of the center of the compensation range and control is performed for this purpose. However, this returning motion results in unnatural image vibrations on completion of panning or tilting which gives the operator a feeling of unnaturalness.
In order to compensate image vibrations based on signals resulting from vibrations to be compensated only, filtering and so on may be performed for separating output signals of the detection apparatus into the signals resulting from the vibrations to be compensated and signals resulting from intentional panning or tilting. In general, however, frequencies of image vibrations range from 0.5 to 30 Hz. Signals resulting from intentional panning and tilting belong to this frequency band as well. It is therefore difficult to completely separate the signals resulting from the vibrations to be compensated and those resulting from intentional panning or tilting.
It is an object of the invention to provide an image vibration compensating apparatus for optimally compensating image vibrations while reducing unnatural image vibrations on completion of intentional panning and tilting.
An image vibration compensating apparatus comprises: a vibration detection means for detecting a vibration causing an image vibration and outputting an signal in accordance with the vibration; a panning and tilting detection means for detecting a start and a stop of intentional panning or tilting; a computing means for subtracting a value for canceling the output signal of the vibration detection means resulting from the intentional panning or tilting from the output signal of the vibration detection means during a period between detection of the start of the intentional panning or tilting and detection of the stop of the intentional panning or tilting by the panning and tilting detection means in a period at least including the instant of the stop of the intentional panning or tilting, for subtracting a value for canceling the output signal of the vibration detection means from the output signal of the vibration detection means in a period after the detection of the stop of the intentional panning or tilting by the panning and tilting detection means and for outputting the output signal of the vibration detection means intact in any other period; and a compensation means for compensating the image vibration based on the output signal of the computing means.
In the image vibration compensating apparatus the vibration detection means detects the vibration causing the image vibration and outputs the signal in response to the vibration. The panning and tilting detection means detects the start and stop of the intentional panning. During the period between detection of the start of the intentional panning or tilting and detection of the stop of the intentional panning or tilting by the panning and tilting detection means, the computing means subtracts the value for canceling the output signal of the vibration detection means resulting from the intentional panning or tilting from the output signal of the vibration detection means in the period at least including the instant of the stop of the intentional panning or tilting. The computing means subtracts the value for canceling the output signal of the vibration detection means from the output signal of the vibration detection means in the period after the detection of the stop of the intentional panning or tilting by the panning and tilting detection means. The computing means outputs the output signal of the vibration detection means intact in any other period. The compensation means compensates the image vibration based on the output signal of the computing means.
Other and further objects, features and advantages of the invention will appear more fully from the following description.